Silver halide emulsion containing a stabilizing combination of an azaidene and a n,n-dialkyl-dithiocarbamic acid ester

ABSTRACT

The stability of photographic silver halide emulsions against the formation of fog is improved by addition of substituted tetra-azaindene or pentaazaindene and N,N-dialkyl-dithiocarbamic acid esters defined herein below.

Unit% 11131 States Patent [191 Himmelmann et al.

SILVER I-IALIDE EMULSION CONTAINING A STABILIZING COMBINATION OF AN AZAIDENE AND A N,N-DIALKYL-DITHIOCARBAMIC ACID ESTER Inventors: Wolfgang I-Iimmelmann, Opladen;

Anita Von Konig; Franz Moll, both of Leverkusen; Wilhelm Saleck, Schildgen, all of Germany AGFA-Gevaert Aktiengesellschaft, Leverkusen, Germany Assignee:

Continuation-impart of Ser. No. l76,326, Aug. 30,

1971, abandoned.

Foreign Application Priority Data Sept. 1, 1970 Germany 2043205 Herz 96/109 Primary ExaminerDavid Klein Assistant Examiner-Won H. Louie, Jr. Attorney, Agent, or FirmConnolly and Hutz [57] ABSTRACT The stability of photographic silver halide emulsions against the formation of fog is improved by addition of substituted tetra-azaindene or pentaazaindene and N,N-dialkyl-dithiocarbamic acid esters defined herein below.

3 Claims, No Drawings SILVER HALIDE EMULSION CONTAINING A STABILIZING COMBINATION OF AN AZAIDENE AND A N,N-DIALKYL-DITIIIOCARBAMIC ACID wherein 1. aryl, especially a group of the phenyl or naphthyl ESTER series, which may be substituted, eg with alkyl, 5 alkoxy, alkylthio, nitro, halogen such as fluorine This application is a continuation-in-part of our coor chlohheior cyahoi pending US. application Set. No. 176,326 filed Aug. up w 18, and preferably p to r- 30, 1971, entitled A Stabilized Photographic Mate- 9" atoms, the alkyl radlcalmay be subsumed rial," now abandoned with cyano, alkylthio, arylthio in particular phe- The invention relates to photographic material com- 10 h or P y sauch as nzyl 0r phenylethyl, prising at least one silver halide emulsion layer, the stawhlch case agam the phenyl radlcal may be bility of which is improved by the addition of Subsmuted under N,N-dialkyl-dithiocarbamic acid esters and tetrao a heterocychc group m pamcular a rmg of the pemwazaindenes. pyrimidine or triazine series, the heterocyclic It is well known that photographic emulsions on storring being optionally Substituted with halogen age become spontaneously developable without expo- Such as fluorine of chlorine or aryl, in Particular sure to light. There is normally a detectable amount of P y or haphthyl, which y be shhsthlltefl as the silver salt reduced during development at unexindicated under alkylamhlo and arylamlhoi posed areas. This phenomenon is commonly called fog -g phenylamino, alkoxy, y. p o y, or chemical fog. Fog depends both upon the nature of and the dialkylamiho'dhhiocarbamic acid group the emulsion and the conditions of development. For a 0f the above formula; given emulsion it increases with the degree of develop- 2 Straight Chained of branched alkyl with P ament. It is common practice to make accelerated tests y p to 3 carbon atoms which y be Substituted, of the stability of photographic emulsions by storage at -2- with cyanoincreased temperature or humidity, or both. It is desir- The Compounds listed in the following tables have able to have emulsions as stable as possible under the been found to e specially Suitable condition of high temperature, which may occur in tropical climates. Fog usually appears over the whole TABLE 1 area of the light-sensitive layer, but when severe is quite frequently non-uniform. Compound Melting It is known that certain compounds particularly hetumber R2 erocyclic mercapto or imino compounds have an anti- 1 '"3233f Mhhyl C foggant and stabilizing effect when incorporated into 2. g-nitm h'ehyi Ethyl 31H photographic silver halide emulsions and so improve 2: j Maggi n greatly the keeping qualities of the emulsions. Mostly 35 f' gggggg f C the so-called fog-inhibitors or stabilizers form diffii y :IdoITIIII 116: C cultly soluble or insoluble silver compounds with the 31:: "I: C silver ions of the photographic emulsion. It is also known that inorganic or organic mercury compounds 12... z itrophen can be used. Many of these stabilizers however, are of 40 iijijjjjjjjjjj 3 1.2 hlr'pitetd1 utility; sti nce they have a desensitizing effect or 15 N Ethyl on a er e gra a ton.

It is among the objects of the invention to provide is 2 ?f Methyl stabilizers which cause no reduction in the sensitivity at 17 concentrations at which they achieve sufficient stabili- 1s 48 c zation. Another object is to provide a photographic sil- T ver halide emulsion that IS stable against the production 19 zsdmethylbemyl do C of fog upon storage and stable with respect to the speed 20 Methyl 2-cyanoethyL. 89 0. a and contrast of the emulsion. Other objects and advan- 21 Imbutyl Methyl -5-33 tages will become apparent from a consideration of the 22 CH(CH) s CH2 CflH5 do 5 5}- following description and examples. i 4

decomp.

A photographic material having at least one silver 23 CmCHh'CHQ'QHE halide emulsion layer has now been found which con- 24 CHI-C04) gz gtains either tetra-azaindene or penta-azaindene and /\/N\ N,N-dialkyl-dithiocarbamic acid esters of the following formula:

R S CS N(R2)2 TABLE 2 N air-f W-s-os-mms N N in Compound number Rs R4 R5 C.)

25 Eth l...

TABLE z cuminued N,N-Dialkyl-dithiocarbamic acid esters are prepared by method known in the literature. Reference may be made to the methods described in Houben-Weyl: Methoden der organischen Chemie," 4th edition, Volume 9, pages 837-845 and .l.Chem.Soc.C., page 466 (1967).

N,N-Dialkyl-dithiocarbamic acid esters together with tetra-, or penta-azaindenes used according to the invention have the advantage over many of the known stabilizers that they do not contain any mercapto groups. The photographic properties such as sensitivity, gradation and clarity are efficiently stabilized by the compounds according to the invention without the graininess or or fog being adversely affected.

Many stabilizers which are particularly effective in preventing fogging cause a reduction in the sensitivity of the fresh material, which is often disadvantageous. Other stabilizers which are just sufficiently effective in preventing an increase in fogging cause a substantial and always disadvantageous change in the sensitivity during storage, and this change is in most cases accompanied by a flattening of the gradation. The N,N-dialkyl-dithiocarbamic acid esters and azaindene combination mentioned here have an excellent stabilizing effect both on the gradation and sensitivity so that these properties remain unchanged over long periods of time. The combination of N,N-dialkyldithiocarbamic acid esters and azaindenes in the emulsion prevents fog after storage of the unprocessed material in a warm moist atmosphere.

The azaindenes and N,N-dialkyl-dithiocarbamic acid esters to be used according to the invention may be added both to the silver halide layers and to other water-permeable layers, e.g., intermediate layers, protective layers or the baryta layer. These compounds may be added to light-sensitive silver halide emulsions out at any stage of preparation of the emulsion preferably before the after-ripening. The N,N-dialkyldithiocarbamic acid esters added may vary within wide limits and quantities of between 0.001 g and 5 g have generally been found sufficient. Particularly advantageous results are obtained when the emulsions contain 1 to 50 mg of the compounds according to the invention per kg of the silver halide emulsion. The tetraazaindenes and penta-azaindenes, which are stabilizers according to this invention, are described in the article by Birr, Z.Wiss. Phot. 47, 2-58 (l952). It has been found that the combination of these azaindenes with N,N-dialkyldithiocarbamic acid esters of the present invention provides a superior stabilizing effect against moist warm conditions, including after a period of storage. Of particular effectiveness is combination with those tetra-, and penta-azaindenes which are substituted with hydroxyl and amino-groups. Tetra-, or pentaazaindenes used according to this invention may be added in an amount sufficient to provide the advantageous results. An amount of 200 mg of azaindene per kg. of emulsion has been found effective.

The compounds according to the invention are advantageously added in the form of solutions. Suitable solvents are e.g. lower alcohols, tetrahydrofuran, acetone or dimethyl formamide.

The usual silver halide emulsions are suitable for the present invention. These may contain silver chloride, silver bromide or mixtures thereof, optionally with a small silver iodide content of up to 10 mols per cent.

The binder used for the photographic layers is perferably gelatine, although this may be partly or completely replaced by other natural or synthetic binders. Suitable natural binders are e.g. alginic acid and its derivatives such 'as salts, esters or amides, cellulose derivatives such as carboxymethyl cellulose, alkyl celluloses such as hydroxyethyl cellulose, starch or its derivatives such as ethers or esters or carragheenates. Suitable synthetic binders are e.g. polyvinyl alcohol, partly saponified polyvinyl acetate or polyvinyl pyrrolidone.

The emulsions may also be chemically sensitized, e.g. by adding compounds which contain sulfur at the stage of chemical ripening, for example allyl isothiocyanate, allyl thiourea or sodium thiosulfate. The chemical sensitizers used may also be reducing agents, e.g. the tin compounds described in Belgian Patent Specifications No. 493,464 and 568,687 or polyamine such as diethylene triamine or aminomethyl sulfonic acid derivatives, e.g. according to Belgian Patent Specification No. 547,3 23.

Noble metals and noble metal compounds, e.g. gold, platinum, palladium, iridium, ruthenium or rhodium, are also suitable chemical sensitizers. This method of chemical sensitization has been described in the article by R. Koslowsky, Z. Wiss. Phot. 46, 65-72 (i).

The emulsions may also be sensitized with polyalkylene oxide derivatives, e.g. with polyethylene oxide which has a molecular weight of between 1000 and 20,000 or with condensation products of alkylene oxides and aliphatic alcohols, glyeols, cyclic dehydration products of hexitols, alkyl substituted phenols, aliphatic carboxylic acids, aliphatic amines, aliphatic diamines and amides. The condensation products have a molecular weight of at least 700, preferably more than 1000. These sensitizers may, of course, be combined for the purpose ofv achieving special effects, as described in Belgian Patent Specification No. 537,278 and in British Patent Specification No. 727,982.

The emulsions may also be optically sensitized, e.g. with the usual polymethine dyes such as neutrocyanines, basic or acid carbocyanines, rhodacyanines, hemicyanines, styryl dyes or oxonoles. Sensitizers of this type are described in the work by F. M. Hamer The Cyanine Dyes and Related Compounds (1964).

In addition to N,N-dialkyl-dithiocarbamic acid esters and tetraor penta-azaindenes, the emulsions may contain other known stabilizers.

The emulsions may be hardened in the usual manner, for example with formaldehyde or halo-substituted aldehydes which contain a carboxyl group, such as mucobromic acid, diketones, methane sulfonic acid esters, dialdehydes.

The emulsions may also contain color couplers in dissolved or dispersed form.

The stabilizers which we have described may be used in various kinds of photographic emulsions. In addition to being useful in X-ray and other non-optically sensip the usual salts. The flocculate is redispersed in warm water, the required quantity of ripe gelatine containing sulfur is added and the emulsion is ripened to optimum sensitivity in the presence of gold(l)-thiocyanate complexes and sodium thiosulfate.

Before the emulsion is heated to the ripening temperature, it is divided into 17 portions. The first portion is ripened without additive, whilst the other portions are treated with one of the compounds shown in the table below.

After chemical ripening, 200 mg of 4-hydroxy-6- methyl-1,3,3A,7-tetraazaindene as stabilizer, 600 mg of saponin as wetting agent and 10 ml of 10 aqueous solution of formaldehyde are added, the amounts being in each case based on 1 kg of emulsion.

The samples are then cast on a cellulose acetate support and dried, exposed in a sensitometer behind a grey step wedge and developed in a developer of the following composition at 20C for 7 minutes and 16 minutes:

Sodium sulfite sicc. 0 borax 7 hydroquinone 3 p-monomethylaminophenol sulfate 3 sodium citrate 7 potassium bromide 0 made up with water to l litre The results of the sensitometric tests are shown in the following table.

Table 3 Com-d Quantity 7 min. development 16 min. development oun o. in mg time time S fog S y fog control 0,95 0,16 1,35 0,22 l 2 0,5 1,00 0,11 0,5 1,35 0,14 2 8 i 1,00 0,14 10 1,40 0,16 4 6 i0,5 0,90 0,14 i0 1,30 0,18 5 3 0,5 0,80 0,14 0 1,40 0,18 l3 l0 0,5 0,90 0,14 0,5 1,20 0,18 15 6 O,5 1,05 0,14 0,5 1,40 0,18 2O 10 i 1,05 0,14 i 1,45 0,18 21 3 i 0 0,95 0,14 :0" 1,40 0,19 23 5 0 1,05 0,13 +0,5 1,40 0,18 24 10 i0 0,80 0,14 0 1,20 0,18 25 3 i 0 0,90 0,10 +0,5 1,40 0,14 26 3 0,5 0,85 0,10 1 0 1,20 0,13 27 3 0,5 0,80 0,10 0,5 1,25 0,12 28 3 0,5 0,85 0,10 0,5 1,35 0,14 31 6 i 0,80 0,11 -0,5 1,20 0,15 34 3 +0,5 0,85 0,10 t 1,15 0,13

3 DIN 1 shutter step I S sensitivity tized emulsions they may also be used in ortho- EXAMPLE 2 chromatic, panchromatic and infrared-sensitive emulsion. They may also be used for emulsions suitable for use in the silver salt diffusion process for colorphotographic emulsions and for photographic materials for the silver dye bleach process.

The following Examples illustrate the invention:

EXAMPLE 1 A very highly sensitive silver iodobromide emulsion containing 6 mols per cent of silver iodide is prepared in the usual manner, the silver nitrate solution being poured into a solution which contains gelatine in addition to KBr and K1. The emulsion is flocculated with ammonium sulfate in a known manner and freed from A highly sensitive silver iodobromide emulsion containing 5 of silver iodide is prepared in the usual manner, the silver nitrate solution being run into a solution which contains gelatine in addition to K1 and KBr. The emulsion is flocculated in a known manner with ammonium sulfate and freed from the soluble salts by washing. The flocculate is redispersed in warm water, the required quantity of ripe gelatine containing sulfur is added, and the emulsion is ripened to the optimum sensitivity in the presence of gold(l)-thiocyanate complexes and sodium thiosulfate. I

200 mg of 4-hydroxy-6-methyl-l ,3,3a,7- tetraazaindene as stabilizer, 600 mg of saponin as wetting agent and 10 ml of a 10 aqueous solution of formaldehyde are then added to the emulsion, the amounts being inveach case based on 1 kg of emulsion. The emulsion is then divided into 18 portions. No additive is added to the first portion and the other portions contain 5 mg/kg of the compounds shown in the following table.

The emulsions are cast on a layer support of cellulose acetate, dried and exposed and developed as described above. Some of the samples are stored at 60C for 3 days and developed at 20C for 16 minutes.

The results of the sensitometric test are shown in the following table. This shown that a definite fog stabilising effect is observed even in the heating cupboard. The substances may therefore be added both before ripening and after chemical ripening as casting addil and with 20 mg of the ortho-chromatic sensitizer:

tives to achieve a distinct improvement in the fog of the 15 emulsion.

Table 4 Development time Development time 3 days heating Compound 7 minutes 6 minutes 16 minutes No. S y Fog S 'y Fog S y Fog control control 0.91 0.22 control 1. l3 0. 30 control 1 12 0.35 (no additive) l +l.0 1.05 0.15 -l-O.4 1.19 0.21 0.5 1.18 0.25 2 +1.0 0.92 0.11 10 1.12 0.20 +0 1.13 0.21 4 10 0.96 0.20 0.5 1.17 0.25 +1 .0 1.19 0.30 5 0.80 0. 18 10 0.92 0.21 10 0.98 0.28 13 10 1.06 0.21 10 1.10 0.26 10 1.10 0.31 14 i) 1.06 019 1.18 0.26 +10 1.22 0.31 15 10 1.02 0.19 0.5 1.12 0.27 10 1.05 0.32 if 1.07 0.20 10 1.09 0.28 405 1.1 1 0.31 21 j)" 1.03 0.20 10 1.10 0.28 1.0 1.18 0.30 23 +0.5 1.20 0.14 10 1.22 0.24 10 1.30 0.27 24 +0.5 1.05 0.15 10 1.13 0.25 10 1.13 0.30 25 10 0.87 0.14 10 1.25 0.24 if 1.29 0.26 26 +0.5 0.93 0.17 10 1.18 0.26 10 1.23 0.29 27 10 0.86 0.18 10 1.22 0.27 1.0 1.31 0.31 28 10 0.88 0.17 10 1.19 0.25 10 1.29 0.28 31 +0.5 0.80 0.15 10 1.20 0.20 10 1 10 0.25 34 10 0.75 0.14 0.5 1.10 0.16 10 1.15 0.18

3= 1 shutter stop EXAMPLE 3 The quantity 18 based on 1 kg of emulsion. The emul- An emulsion as described in Example 1 is divided up so that 1 part serves as comparison example without sion samples are cast on a layer support of cellulose acetate and treated in the same way as described in Example 2. The results are shown in the following table.

Table 5 Development time Development time 3 days heating com- 7 minutes 16 minutes 16 minutes pound No. Quantity S. 'y Fog S -y Fog S 7 Fog blank no additive 0.75 0.14 1.10 0.20 -1.0 0.90 0.25

1 5 mg before after- +1.0 0.70 0.10 +0.5 1.00 0.13 +0 0.90 0.17

ripening l 5 mg as casting +1 .0 0.80 0.1 1 10 1.10 0.16 1.00 0.20

additive 14 5 mg before alter- 10 0.75 0.12 10 1.15 0.14 0.5 1.05 0.17

ripening 14 5 mg as casting 10 0.85 0.13 0.5 1.20 0.14 10 1. 10 0.18

additive 23 5 mg before atter- +0.5 0.90 0.12 +0.5 1.25 0.15 10 1.15 0.17

ripening 23 5 mg as casting +O.5 0.85 0.1 1 10 1.10 0.13 +0.5 0.90 0.14

additive 25 5 mg before after- 10 0.70 0.09 fl1 1.00 0.1 1 -10.S 0.95 0.13

ripening 25 5 mg as casting +0.5 0.95 0.12 10 1.30 0.15 10 1.20 0.17

additive additive and the other part of the emulsion is treated with compounds according to the invention either at the stage of after-ripening or when the emulsion is ready for casting. All the emulsion samples are panchromatically sensitized with 40 mg of the panchromatic sensitizer of the formula:

Among other advantages provided by the combination of N,N-dialkyl-dithiocarbamic acid esters and the azaindenes is the prevention of fog after storage of the unprocessed material in a warm moist atmosphere. An emulsion, which does not contain the stabilizer combination, after subjection to moist warm treatment in the unprocessed state and then developed exhibits an extremely high fog value and/or decreased S and gamma values, particularly when compared with a corresponding emulsion containing the combination of azaindene and N,N-dialkyl-dithiocarbamic acid ester.

Accordingly, it is a feature of the present invention that a silver halide emulsion containing the combination of tetraor penta-azaindene and N,N-dialkyldithiocarbamic acid ester is stabilized against moist warm conditions over a period of time, even though unprocessed.

What is claimed is:

1. A photographic element having at least one lightsensitive silver halide emulsion layer which a stabilizing amount of an azaindene selected from the. group consisting of tetra or penta azaindene substituted with hydroxyl or amino groups and a N,N dialkylthiocarbamic acid ester of the following formula:

2. The light-sensitive photographic material of claim, 1 wherein R represents an alkyl radical having 1 to 3' carbon atoms.

3. The photographic element as claimed in claim 1 wherein 4-hydroxy-6-methyll ,3 ,3a,7-tetraazaindene is the azaindene.

"ZS/23% UNITED STATES PATENT OFFICE CERTIFICrTE 0F CORRECTI Patent No. 738543954- DaterL December 1971;;

0 I- .L Inventor) Wolfgano Hlrrmelmenn et 8.1

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown belowr Column 2, Table l, the R substituent of compound 13 should read as follows: -CH -CH(CN)-S-C H Column 2, Table l, the R substituent of compound 22 should read as follows: -CH(CN)-S-CH -C H In the Title, "Azaidene" should read Azaindene In the "Inventors "Q should read Anita von Kdnig Signed and sealed this 13th day of May 1975.

'(SEAL) Attest:

C. MARSHALL DANN v RUTH C. MASON Co;nmissioner. of Patents Attesting Officer and Trademarks 

1. A PHOTOGRAPHIC ELEMENT HAVING AT LEAST ONE LIGHTSENSITIVE SILVER HALIDE EMULSION LAYER WHICH A STABILIZING AMOUNT OF AN AZAINDENE SELECTED FROM THE GROUP CONSISTING OF TETRA OR PENTA AZAINDENE SUBSTITUTED WITH HYDROXYL OR AMINO GROUPS AND N, N-DIALKYLTHIOCARBAMIC ACID ESTER OF THE FOLLOWING FORMULA:
 2. The light-sensitive photographic material of claim 1 wherein R2 represents an alkyl radical having 1 to 3 carbon atoms.
 3. The photographic element as claimed in claim 1 wherein 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene is the azaindene. 